Prior art workers have devised numerous types of patch systems. In their simplest form, prior art patch systems comprised absorbent patches of woven or nonwoven synthetic or natural fibers affixed directly to an adhesive tape and, in many instances, protected by release papers. In similar structures, an impervious layer of cellophane, or the like, was located between the patch and the adhesive tape. In many of these prior art structures, the sample material applied to the patch system came into contact with the tape. Many of these systems were limited as to the type of tape which could be used and frequently, the tape would not adhere well, particularly in the presence of water, perspiration, or the like. Often the tape was more irritating and would gap easily so that the patch system was non-occlusive. The sample material applied to such structures would frequently dry out rapidly.
In an attempt to provide a more occlusive patch system and to prevent the sample from being in contact with the tape, prior art workers have developed various types of small, dish-like housings having a continuous skin-contacting edge. These housings have generally been made of metal such as aluminum and the like. These structures, however, have been characterized by certain disadvantages such as being rigid, too thick and having limited sample volume. A recent example of such structures is taught in U.S. Pat. No. 4,158,359. This patent teaches a single or multi-piece housing containing an absorbent pad and having peripheral edges which are turned inwardly or outwardly so as to form a continuous seal with the skin. One embodiment of this patent comprises a housing having outwardly rolled edges with an additional annular member adapted to form a second seal and to retain an absorbent pad within the housing. The housing of this patent is affixed to an adhesive covering sheet and is surrounded by an annular porous protecting sheet. The housing of this reference has a limited sample volume and is generally rigid, being made of metal or a synthetic resin.
U.S. Pat. No. 4,450,844 is directed to a patch system which overcomes the above noted deficiencies of earlier prior art patch systems and which is substantially completely occlusive to render tests, for example, more sensitive and reproducible. This is accomplished by means of a pair of integral, parallel, spaced, continuous, skin-contacting edges of the housing having an air space therebetween, and by virtue of the fact that the housing is made of soft and flexible material.
The sample material applied by way of the patch system of U.S. Pat. No. 4,450,844 does not contact the adhesive of the tape which mounts the housing and different types of tape can be used, such as hypo-allergenic tapes. The housing, which is made of non-toxic, inert material, provides good sample retention indefinitely and can be used with or without an absorbent pad. Various sizes of housings and absorbent pads can be used and the system permits modifications of patch testing procedures not possible with earlier prior art systems.
The patch system of U.S. Pat. No. 4,450,844 works well even in the presence of perspiration and one to whom the patch system is applied can swim and shower. When used for test purposes, the patch system (with sample applied) can be prepared ahead of time, in the laboratory and taken to the test site, ready for use. This patch system provides a technique which may reduce the number of visits for panelists during testing. The system further enables measurement of the amount of sample before and after application to a panelist, which is useful in controlled investigations of new drugs. Finally, the system can be used as single patches or made into strips containing a plurality of housings.
The present invention is based upon the discovery that the patch system of U.S. Pat. No. 4,450,844 can be markedly improved by providing the housing with a planar flange about its periphery, spaced slightly above the one or more skin-contacting edges of the housing. The flange extends outwardly from the exterior surface of the housing and is provided with a layer of adhesive on its bottom surface so that the flange is used to adhere the housing to the skin. Prior to use, the housing and its peripheral flange may be provided with a protective release paper.
The improved system eliminates the need of a cover sheet in the form of an adhesive coated tape to affix the housing to the skin. It is less expensive to manufacture and is easier to manipulate. Channeling is substantially reduced or eliminated. Finally, the patch system of the present invention has an aesthetically more pleasing appearance.
The patch system of the present invention has numerous applications. For example, it can be used in conventional predictive patch testing and in diagnostic testing (for example, by dermatologists and allergists to determine what is the causative agent for a patient's skin reaction). The patch system can also be used as a dermal drug delivery vehicle. The housing will hold a sufficient quantity of drug to allow the drug to be gradually absorbed through the skin for certain treatments such as an anesthetic patch for a painful procedure. The patch system is suitable for use both with humans and animals.